Light source device and endoscope apparatus comprising the same

ABSTRACT

A light source device includes a first semiconductor light source, a second semiconductor light source, and a wavelength converter. The first semiconductor light source emits light in a first wavelength range. The second semiconductor light source emits light in a second wavelength range different from the first wavelength range. The wavelength converter absorbs the light in the first wavelength range to emit light in a third wavelength range different from either of the first wavelength range and the second wavelength range, and transmits the light in the second wavelength range substantially entirely.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2007-335321, filed Dec. 26, 2007,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light source device.

2. Description of the Related Art

Currently, an endoscope apparatus performs, in addition to ordinaryobservation using white light, a narrow band imaging, that is, anobservation scheme in which the visibility of a lesion part or the likeis improved using light having a specific wavelength. The endoscopeapparatus having such a function is, more specifically, configured toswitch between white light for ordinary observation and light having aspecific wavelength for narrow band imaging, which is referred asspecial light hereinafter, projecting selected light from the endportion of an endoscope.

Jpn. Pat. Appln. KOKAI Publication No. 2006-026128 discloses a lightsource device for such an endoscope apparatus. In this light sourcedevice, a unit including a light-deflecting element is slid so that thelight-deflecting element is arranged on an optical path as required,which performs switching between the white light for ordinaryobservation and the special light, in other words, switching theprojection light colors.

Since switching between the white light and special light is performedby sliding the unit, the light source device described above requires amechanism for sliding the unit. This results in a bulky, complicateddevice.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of this situation, and ashas its object to provide a compact light source device that can switchthe projection light colors.

A light source device according to the present invention includes afirst semiconductor light source, a second semiconductor light source,and a wavelength converter. The first semiconductor light source emitslight in a first wavelength range. The second semiconductor light sourceemits light in a second wavelength range different from the firstwavelength range. The wavelength converter absorbs the light in thefirst wavelength range to emit light in a third wavelength rangedifferent from either of the first wavelength range and the secondwavelength range, and transmits the light in the second wavelength rangesubstantially entirely.

According to the present invention, a compact light source device thatcan switch the projection light colors is provided.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Advantages of the invention may berealized and obtained by means of the instrumentalities and combinationsparticularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 shows a light source device according to the first embodiment ofthe present invention;

FIG. 2 shows the spectrum characteristics of YAG:Ce;

FIG. 3 shows the spectrum characteristics of Ce-activated Ca₃Sc₂Si₃O₁₂;

FIG. 4 shows a light source device according to the second embodiment ofthe present invention;

FIG. 5 shows a multi-phosphor unit shown in FIG. 4;

FIG. 6 shows another type of multi-phosphor unit, which can replace themulti-phosphor unit shown in FIG. 5;

FIG. 7 shows the emission spectrum of Eu-activated La₂O₂S;

FIG. 8 shows the emission spectrum of Eu, Mn-activated BaMgAl₁₀O₁₇;

FIG. 9 shows the emission spectrum of Eu-activated BaMgAl₁₀O₁₇;

FIG. 10 shows a light source device according to the third embodiment ofthe present invention;

FIG. 11 shows the spectrum characteristics of SrAlO:Eu;

FIG. 12 shows the spectrum of light projected from the phosphor unit ofa light source device according to the fourth embodiment of the presentinvention;

FIG. 13 schematically shows a general endoscope apparatus; and

FIG. 14 shows the arrangement of an endoscope end portion shown in FIG.13.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention will be described withreference to the accompanying drawing.

First Embodiment

FIG. 1 shows a light source device according to the first embodiment ofthe present invention. As shown in FIG. 1, a light source device 10 hasa first light source 20A, a second light source 20B, an optical fiber30A to guide light projected from the first light source 20A, an opticalfiber 30B to guide light projected from the second light source 20B, aphotocoupler 40 connected to the optical fibers 30A and 30B, an opticalfiber 50 to guide light output from the photocoupler 40, and awavelength converter 60 to emit illumination light corresponding to thelight guided by the optical fiber 50.

The first light source 20A has a first semiconductor laser 22A, a lens24 to converge divergent light emitted from the first semiconductorlaser 22A, and a connecting element 26 to optically connect the lightconverged by the lens 24 to the optical fiber 30A. Similarly, the secondlight source 20B has a second semiconductor laser 22B, a lens 24 toconverge divergent light emitted from the second semiconductor laser22B, and a connecting element 26 to optically connect the lightconverged by the lens 24 to the optical fiber 30B.

The light source device 10 further has a driving circuit 82A to switchlight on and light off of the first semiconductor laser 22A, that is,turns on and off the first semiconductor laser 22A independently, and adriving circuit 82B to switch light on and light off of the secondsemiconductor laser 22B, that is, turns on and off the secondsemiconductor laser 22B independently.

The photocoupler 40 comprises a two-input, one-output optical fibercoupler 42, which has two incident ends and one exit end. One incidentend of the optical fiber coupler 42 is optically connected to the firstlight source 20A through the optical fiber 30A. The other incident endof the optical fiber coupler 42 is optically connected to the secondlight source 20B through the optical fiber 30B. The exit end of theoptical fiber coupler 42 is optically connected to the wavelengthconverter 60 through the optical fiber 50.

The photocoupler referred to here is what serves to optically connectlight from incident ends to at least one exit end, and its connectionstructure is not limited at all. For example, the photocoupler may beone fabricated by removing the claddings of two or more optical fibersrespectively partially, and then heating and pressing the optical fibersin contact with each other, thus connecting the cores of the opticalfibers. Alternatively, the photocoupler may be one fabricated bybringing the ends of parallel optical fibers into contact with the endof another optical fiber that opposes them, and heating the resultantstructure, thus connecting the optical fibers to the opposing opticalfiber. In these two examples, the connecting portion may be called partof the photocoupler, or the connecting portion itself may be called thephotocoupler. In either case, the incident optical fibers to guideincident Tight to the connecting portion can be called incident opticalfibers connected to the incident end of the photocoupler, and the exitoptical fiber to guide light emerging from the connecting portion to theexit end can be called an exit optical fiber connected to the exit endof the photocoupler.

The first semiconductor laser 22A emits blue laser light having awavelength of 460 nm, and the second semiconductor laser 22B emitsviolet laser light having a wavelength of 415 nm. The wavelengthconverter 60 comprises a phosphor unit 62 including a phosphor of Ce(cerium)-activated YAG (yttrium-aluminum-garnet) (to be referred to asYAG:Ce hereinafter). FIG. 2 shows the spectrum characteristics ofYAG:Ce. In FIG. 2, the broken line represents the absorption spectrum ofYAG:Ce, and the solid line represents its emission spectrum. As shown inFIG. 2, the absorption spectrum of YAG:Ce has its peak near 460 nm. Theabsorption range of the absorption spectrum is defined as a wavelengthrange where the absorption strength of the absorption spectrum of agiven phosphor is half or more the peak value. The absorption range ofthe absorption spectrum of YAG:Ce is approximately 430 nm to 480 nm. Thephosphor unit 62 absorbs 460-nm wavelength blue light emitted from thefirst semiconductor laser 22A to emit light having a wavelength ofapproximately 530 nm, but almost entirely transmits the 415-nmwavelength violet light emitted from the second semiconductor laser 22B.

The operation of the light source device according to this embodimentwill be described.

First, operation that takes place when the first semiconductor laser 22Ais turned on will be described. When the first semiconductor laser 22Ais turned on, it emits 460-nm wavelength blue laser light. A beam of thelaser light emitted from the first semiconductor laser 22A is convergedby the lens 24 and then enters the optical fiber 30A. The laser lightentering the optical fiber 30A is guided through the optical fiber 30A,travels through the optical fiber coupler 42, is guided through theoptical fiber 50, and enters the phosphor unit 62. As is understood fromFIG. 2, the 460-nm wavelength blue laser light is light within theabsorption range of YAG:Ce. Thus, part of the blue laser light enteringthe phosphor unit 62 is wavelength-converted by YAG:Ce in the phosphorunit 62 into broad-spectrum yellow light having a peak near a wavelengthof 530 nm. The wavelength-converted yellow light is projected from theexit end of the phosphor unit 62. Part of the remaining blue laser lightentering the phosphor unit 62 passes through the phosphor unit 62without wavelength conversion and is projected from the exit end of thephosphor unit 62. Consequently, the yellow light wavelength-converted bythe phosphor unit 62 and the blue light emitted from the semiconductorlaser 22A are projected from the exit end of the phosphor unit 62. Inthis embodiment, the yellow light and blue light are adjusted to formwhite light when mixed. As a result, white light is projected from theexit end of the phosphor unit 62. More specifically, when the firstsemiconductor laser 22A is turned on, white light as observation lightfor ordinary observation is projected from the exit end of the phosphorunit 62.

Subsequently, operation that takes place when the second semiconductorlaser 22B is turned on will be described. When the second semiconductorlaser 22B is turned on, it emits 415-nm wavelength violet laser light. Abeam of the laser light emitted from the second semiconductor laser 22Bis converged by the lens 24 and then enters the optical fiber 30B. Thelaser light entering the optical fiber 30B is guided through the opticalfiber 30B, travels through the optical fiber coupler 42, is guidedthrough the optical fiber 50, and enters the phosphor unit 62. As isunderstood from FIG. 2, the 415-nm wavelength violet laser light is notincluded in the absorption range of YAG:Ce, and is accordingly hardlyabsorbed by YAG:Ce of the phosphor unit 62. Thus, the violet laser lightentering the phosphor unit 62 passes through it almost entirely and isprojected from its exit end. More specifically, when the secondsemiconductor laser 22B is turned on, 415-nm wavelength violet light asobservation light for special observation is projected from the exit endof the phosphor unit 62.

In this manner, the light projected from the phosphor unit 62 when onlythe first semiconductor laser 22A is turned on and the light projectedfrom the phosphor unit 62 when only the second semiconductor laser 22Bis turned on have different colors.

In the light source device 10 of this embodiment, when one of the firstand second semiconductor lasers 22A and 22B is selectively turned on,the white light as the observation light and the 415-nm wavelengthviolet light as the special light are switched without using any movablemechanism such as a slide guide unit, and the selected light isprojected from the same exit end of the phosphor unit 62.

By combining the two semiconductor lasers 22A and 22B, photocoupler 40,and wavelength converter 60, a light source device that can performswitching between white light and violet light easily is fabricated.Since this light source device has a simple structure with no movablemechanism, it is suitable for downsizing.

In this embodiment, the 415-nm wavelength violet light is selectedbecause it is largely absorbed by hemoglobin in the blood and thusfacilitates observation of a blood vessel. However, the presentinvention is not limited to the light having this wavelength, but anylight having a wavelength matching the observation object may beselected. More specifically, for YAG:Ce, light having a wavelength of430 nm or less or light having a wavelength of 480 nm or more may beemployed.

The phosphor is not limited to YAG:Ce but any other appropriate phosphorsuch as a phosphor of Ce-activated Ca₃Sc₂Si₃O₁₂ may be employed. FIG. 3shows the spectrum characteristics of Ce-activated Ca₃Sc₂Si₃O₁₂. In FIG.3, the broken line represents the absorption spectrum, and its solidline represents the emission spectrum. As shown in FIG. 3, theabsorption range of Ce-activated Ca₃Sc₂Si₃O₁₂ is approximately 460 nm to530 nm. Hence, when using this phosphor, the wavelength of theexcitation light of the first semiconductor laser 22A may be set to,e.g., approximately 500 nm, so that the excitation light iswavelength-converted more efficiently to obtain bright illuminationlight.

Second Embodiment

A light source device according to the second embodiment will bedescribed with reference to FIGS. 4 to 9. In the second embodiment, adescription on portions that are common with their equivalents in thefirst embodiment will not be repeated, and portions that are differentfrom their equivalents will mainly be made.

FIG. 4 shows a light source device according to the second embodiment.As shown in FIG. 4, when compared to the light source device 10 of thefirst embodiments a light source device 10A according to the secondembodiment has a third light source 20C in place of the first lightsource 20A, an optical fiber 30C in place of the optical fiber 30A, anda phosphor unit 62A in place of the phosphor unit 62. The third lightsource 20C has a third semiconductor laser 22C, a lens 24 to convergedivergent light emitted from the third semiconductor laser 22C, and aconnecting element 26 to optically connect the light converged by thelens 24 to the optical fiber 30C. The light source device 10A also has,in place of the driving circuit 82A, a driving circuit 82C to switchlight on and light off of the third semiconductor laser 22C, that is,turns on and off the third semiconductor laser 22C independently. Exceptfor this, the arrangement of the second embodiment is the same as thatof the first embodiment.

The third semiconductor laser 22C emits near-ultraviolet light having awavelength of 375 nm. The phosphor unit 62A comprises a multiphosphorunit including different types of phosphors having differentcompositions. FIG. 5 shows the phosphor unit 62A shown in FIG. 4. Asshown in FIG. 5, the phosphor unit 62A comprises the multiphosphor unitformed by stacking a region 66A including R phosphors 64A to emit redlight, a region 66B including G phosphors 64B to emit green light, and aregion 66C including B phosphors 64C to emit blue light sequentiallyfrom the incident end side to the exit light source. As the phosphors64A, 64B, and 64C, those that respectively emit red light, green light,and blue light upon being excited by 375-nm light as near-ultravioletlight are selected. For example, such phosphors 64A, 64B, and 64C may beEu-activated La₂O₂S (red), Eu, Mn-activated BaMgAl₁₀O₁₇ (green), andEu-activated BaMgAl₁₀O₁₇ (blue), respectively. FIG. 7 shows the emissionspectrum of Eu-activated La₂O₂S (red), FIG. 8 shows the emissionspectrum of Eu, Mn-activated BaMgAl₁₀O₁₇ (green), and FIG. 9 shows theemission spectrum of Eu-activated BaMgAl₁₀O₁₇ (blue). As shown in FIGS.7 to 9, the absorption ranges of these phosphors are 270 nm to 400 nm,230 nm to 400 nm, and 270 nm to 410 nm, respectively. The absorptionrange of the multiphosphor unit including these phosphors can beregarded as the overlapping range of the absorption ranges of all thephosphors, which is 270 nm to 400 nm.

The operation of the light source device according to the secondembodiment will be described.

When the third semiconductor laser 22C is turned on, it emits 375-nmwavelength near-ultraviolet laser light. A beam of near-ultravioletlaser light emitted from the third semiconductor laser 22C is convergedby the lens 24 and enters the optical fiber 30C. The laser lightentering the optical fiber 30C is guided through the optical fiber 30C,travels through an optical fiber coupler 42, is guided through anoptical fiber 50, and enters the phosphor unit 62A. As shown in FIG. 5,in the phosphor unit 62A, the region 66A including the R phosphors 64Ato emit red light, the region 66B including the G phosphors 64B to emitgreen light, and the region 66C including the B phosphors 64C to emitblue light are arranged sequentially from the incident end sideconnected to the optical fiber 50. The 375-nm wavelength light emittedfrom the third semiconductor laser 22C is light within the absorptionrange of the multiphosphor unit constituting the phosphor unit 62A.Thus, part of the near-ultraviolet light entering the region 66A iswavelength-converted by the R phosphors 64A into red light, and the redlight enters the region 66B. Part of the remaining near-ultravioletlight entering the region 66A passes through the region 66A and entersthe region 66B. Part of the near-ultraviolet light entering the region66B is wavelength-converted by the G phosphors 64B into green light, andthe green light enters the region 66C. As the G phosphors 64B do notabsorb red light, the red light entering the region 66B passes throughthe region 66B. Therefore, red light, green light, and near-ultravioletlight enter the region 66C including the B phosphors 64C. Thenear-ultraviolet light entering the region 66C is wavelength-convertedby the B phosphors 64C into blue light almost entirely. As the Bphosphors 64C do not absorb red light and green light, the red light andgreen light entering the region 66C pass through the region 66C. As aresult, white light as a mixture of the red light, green light, and bluelight is projected from the exit end of the phosphor unit 62A.

When the second semiconductor laser 22B is turned on, it emits 415-nmwavelength violet laser light. A beam of light emitted from the secondsemiconductor laser 22B is converged by a lens 24, enters an opticalfiber 30B, is guided through the optical fiber 30B, travels through theoptical fiber coupler 42, is guided through the optical fiber 50, andenters the phosphor unit 62A, as described in the first embodiment. The415-nm wavelength violet light is not light within the absorption rangeof the multi-phosphor unit. Thus, the violet light entering the phosphorunit 62A is hardly absorbed by the R phosphors 64A, G phosphors 64B, orB phosphors 64C, but passes through the phosphor unit 62A and isprojected from the exit end of the phosphor unit 62A.

As a result, the light source device 10A projects white light when thethird semiconductor laser 22C is selectively turned on, and 415-nmwavelength violet light when the second semiconductor laser 22B isturned on. As the white light projected from the light source device 10Ahas components of red light, green light, and blue light, it formsillumination light having higher color rendering properties whencompared to the first embodiment. More specifically, according to thesecond embodiment, a light source device having the same advantages asand better color rendering properties than those of the first embodimentis fabricated.

In the second embodiment, as shown in FIG. 5, the phosphor unit 62Acomprises a multiphosphor unit formed by stacking the region 66Aincluding the R phosphors 64A, the region 66B including the G phosphors64B, and the region 66C including the B phosphors 64C. Alternatively, asshown in FIG. 6, the phosphor unit 62A may comprise another type ofmultiphosphor unit in which all of the phosphors 64A, 64B, and 64C aremixed. This simplifies the phosphor unit 62A.

Third Embodiment

A light source device according to the third embodiment will bedescribed with reference to FIG. 10. In the third embodiment, adescription on portions that are common with their equivalents in thefirst embodiment will not be repeated, and portions that are differentfrom their equivalents will mainly be described.

FIG. 10 shows the light source device according to the third embodiment.As shown in FIG. 10, a light source device 10B according to thisembodiment comprises a two-input, two-output optical fiber coupler 42A,which has two incident ends and two exit ends. Two optical fibers 50 andtwo phosphor units 62 are connected to the two exit ends of the opticalfiber coupler 42A. The third embodiment is different from the firstembodiment in these respects.

The optical fiber coupler 42A has the two incident ends and two exitends. The optical fiber coupler 42A distributes light entering oneincident end to the two exit ends with substantially equal lightintensity proportions, and light entering the other incident end to thetwo exit ends with substantially equal light intensity proportions. Awavelength converter 60 has the two phosphor units 62. The two phosphorunits 62 are optically connected to the two exit ends of the opticalfiber coupler 42A, respectively through the two optical fibers 50. Thetwo phosphor units 62 have substantially equal wavelength conversioncharacteristics.

The 460-nm wavelength blue light emitted from the first semiconductorlaser 22A is guided through the optical fiber 30A and enters the opticalfiber coupler 42A. The blue light entering the optical fiber coupler 42Ais distributed by the optical fiber coupler 42A to the two opticalfibers 50 with substantially equal intensities. The blue lightdistributed to the two optical fibers 50 are respectively guided throughthe two optical fibers 50 and enter the two phosphor units 62. The bluelight entering each phosphor unit 62 forms white light in which bluelight and wavelength-converted yellow light are mixed, and the whitelight is projected from the corresponding phosphor unit 62, as describedin the first embodiment.

The 415-nm wavelength violet light emitted from the second semiconductorlaser 22B is guided through the optical fiber 30B and enters the opticalfiber coupler 42A. The violet light entering the optical fiber coupler42A is distributed by the optical fiber coupler 42A to the two opticalfibers 50 with almost equal intensities. The violet light distributed tothe two optical fibers 50 are respectively guided through the twooptical fibers 50 and enter the two phosphor units 62. The violet lightentering each phosphor unit 62 is directly projected from it, asdescribed in the first embodiment.

According to this embodiment, a light source device that has theadvantages of the first embodiment and can illuminate the observationtarget from two directions is fabricated. For example, as in anendoscope apparatus, when the observation target is very close to thelight source, illumination from only one direction may form a shadow,making the observation target difficult to observe. When the exit endsof two phosphor units are arranged to illuminate the observation targetfrom two directions, the observation target will not form a shadoweasily. As a result, a light source device that is more suitable forobservation is fabricated without making the apparatus bulky.

According to this embodiment, each phosphor unit of the wavelengthconverter 60 comprises the phosphor unit 62 described in the firstembodiment. Alternatively, each phosphor unit may comprise themultiphosphor unit 62A described in the second embodiment. Also, thephotocoupler 40 may be changed to an optical fiber coupler having threeor more output ends, and the three or more output ends of the opticalfiber coupler may be respectively connected to phosphor units andoptical fibers corresponding in number to the output ends of the opticalphotocoupler.

Fourth Embodiment

A light source device according to the fourth embodiment will bedescribed. The light source device according to this embodimentbasically has an arrangement identical to that of the first embodiment,but is different from the first embodiment in that a wavelengthconverter 60 comprises a phosphor unit including two types of phosphorshaving different excitation wavelength characteristics.

A phosphor unit 62 according to this embodiment comprises a phosphorunit including the first phosphor that wavelength-converts blue laserlight emitted from a first semiconductor laser 22A but hardlywavelength-converts violet laser light emitted from a secondsemiconductor laser 22B, and the second phosphor that does notwavelength-convert the blue laser light emitted from the firstsemiconductor laser 22A but wavelength-converts the violet laser lightemitted from the second semiconductor laser 22B.

In this embodiment, for example, the first phosphor comprises YAG:Ce,and the second phosphor comprises Eu-activated SrAl₂O₄ (to be describedas SrAlO:Eu hereinafter). FIG. 2 shows the spectrum characteristics ofYAG:Ce, and FIG. 11 shows the spectrum characteristics of SrAlO:Eu. Theabsorption range of YAG:Ce as the first phosphor is 430 nm to 480 nm,and the absorption range of SrAlO as the second phosphor is 270 nm to430 nm.

The operation of the fourth embodiment will be described.

Operation that takes place when the first semiconductor laser 22A isturned on will be described first. As described in the first embodiment,the first semiconductor laser 22A emits 460-nm wavelength blue laserlight. The laser light emitted from the first semiconductor laser 22A isguided through an optical fiber 30A, travels through an optical fibercoupler 42, is guided through an optical fiber 50, and enters thephosphor unit 62. The phosphor unit 62 includes YAG:Ce having thecharacteristics shown in FIG. 2 and SrAlO:Eu having the characteristicsshown in FIG. 11. The 460-nm wavelength blue light is light within theabsorption range of YAG:Ce and outside the absorption range of SrAlO:Eu.Hence, the blue light entering the phosphor unit 62 is efficientlywavelength-converted by YAG:Ce into yellow light having a wavelength ofapproximately 530 nm, but is hardly wavelength-converted by SrAlO:Eu.Consequently, white light as a mixture of the blue light and the yellowlight, which is wavelength-converted by YAG:Ce, is projected from theexit end of the phosphor unit 62.

Operation that takes place when the second semiconductor laser 22B isturned on will be described. As described in the first embodiment, thesecond semiconductor laser 22B emits 415-nm wavelength violet laserlight. The laser light emitted from the second semiconductor laser 22Bis guided through an optical fiber 30B, travels through the opticalfiber coupler 42, is guided through the optical fiber 50, and enters thephosphor unit 62. The 415-nm wavelength violet light is light within theabsorption range of SrAlO:Eu and outside the absorption range of YAG:Ce.Hence, the violet light entering the phosphor unit 62 is hardlywavelength-converted by YAG:Ce, but is efficiently wavelength-convertedby SrAlO:Eu into green light having a wavelength of approximately 540nm. Consequently, as shown in FIG. 12, light as a mixture of 415-nmwavelength violet light and 540-nm wavelength green light is projectedfrom the exit end of the phosphor unit 62. The wavelengths of the mixedlight generally coincide with the absorption wavelengths of hemoglobin,so that the mixed light is suitable for observation of the blood vesselwith a high contrast.

According to this embodiment, a light source device that has theadvantages of the first embodiment and is suitable for observation of ablood vessel or the like with a high contrast is fabricated. In thislight source device, merely the number of types of phosphors included inthe phosphor unit 62 increases and no other major change is needed.Hence, the apparatus does not become bulky.

<Note>

Although the light source comprises a semiconductor laser in all theembodiments described above, the light source is not limited to this,but can comprise another semiconductor light source such as alight-emitting diode. When a light-emitting diode is used, a lessexpensive light source device is fabricated than a case in which asemiconductor laser is used.

The light source device according to any embodiment descried above isparticularly suitably mounted in an endoscope apparatus.

FIG. 13 schematically shows a general endoscope apparatus. As shown inFIG. 13, an endoscope apparatus 100 has a control unit 110, an insertingportion 120 extending from the control unit 110, and an endoscope endportion 130 located at the end of the inserting portion 120. Inobservation using such an endoscope apparatus 100, the observationtarget is close to the endoscope end portion 130. If the exit positionof ordinary observation light is shifted from that of special light,inconveniences such as color separation occur. In contrast to this, withthe light source device according to any one of the embodimentsdescribed above, the exit position of ordinary observation lightcoincides with that of special light, so color separation does notoccur. Thus, this light source device is particularly suitably mountedin an endoscope apparatus.

FIG. 14 shows the arrangement of a general endoscope end portion 130. Asshown in FIG. 14, the endoscope end portion 130 has three end metalmembers 132A, 132B, and 132C, and a cover 144 that covers them. The twoend metal members 132A and 132C are connected to each other through aheat-insulating material 134A, and the two end metal members 132B and132C are connected to each other through a heat-insulating material134B. The end metal member 132C is provided with a solid-state imagesensor 136, an air/water supply nozzle 138, and a suction channel 140.The end metal members 132A and 132B are respectively provided withillumination light guide units 142.

In this manner, the endoscope apparatus generally has the two lightguide units 142. When mounting the light source device of any embodimentdescribed above in the endoscope apparatus, two light source deviceseach having one light-emitting portion may be built into the endoscopeapparatus, as shown in FIGS. 1 and 4, or only one light source devicehaving two light-emitting portions may be built into the endoscopeapparatus, as shown in FIG. 10.

When mounting the light source device of any embodiment described abovein the endoscope apparatus, the wavelength converter 60 may be arrangednear the endoscope end portion 130, or light projected from thewavelength converter 60 may be guided to the endoscope end portion 130through another optical fiber. The former arrangement is preferable forobtaining high-luminance illumination light. The latter arrangement ispreferable for suppressing heat generation near the endoscope endportion because a phosphor unit that emits heat is arranged away fromthe endoscope end portion.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A light source device comprising: a first semiconductor light sourceto emit light in a first wavelength range; a second semiconductor lightsource to emit light in a second wavelength range different from thefirst wavelength range; and a wavelength converter to absorb the lightin the first wavelength range to emit light in a third wavelength rangedifferent from either of the first wavelength range and the secondwavelength range, and to transmit the light in the second wavelengthrange substantially entirely.
 2. The device according to claim 1,wherein the light in the third wavelength range has a wavelength longerthan that of the light in the first wavelength range, the device furthercomprises a first light source driving circuit to switch light on andlight off of the first semiconductor light source independently, and asecond light source driving circuit to switch light on and light off ofthe second semiconductor light source independently, and firstillumination light projected from the wavelength converter when only thefirst semiconductor light source is turned on and second illuminationlight projected from the wavelength converter when only the secondsemiconductor light source is turned on have different colors.
 3. Thedevice according to claim 2, further comprising a photocoupler includinga first incident end and a second incident end that are opticallyconnected to the first semiconductor light source and the secondsemiconductor light source, respectively, and at least one exit end thatis optically connected to the wavelength converter.
 4. The deviceaccording to claim 2, wherein the first illumination light compriseswhite light, and the second illumination light comprises light with acolor substantially the same as that of the light in the secondwavelength range.
 5. The device according to claim 1, wherein thewavelength converter includes a first phosphor, and the first wavelengthrange comprises an absorption range of an absorption spectrum of thefirst phosphor.
 6. The device according to claim 5, wherein the firstphosphor comprises cerium-activated yttrium-aluminum-garnet, the firstwavelength range comprises a range of 430 nm to 480 nm, and the secondwavelength range comprises a range of not more than 430 nm and/or notless than 480 nm.
 7. The device according to claim 1, wherein thewavelength converter includes different types of phosphors havingdifferent composition, the different types of phosphors being selectedso as to absorb the light in the first wavelength range to emit lighthaving wavelengths that are longer than that of the light in the firstwavelength range and different from each other, and the first wavelengthrange comprises an overlapping range of absorption ranges of absorptionspectra of the different types of phosphor materials.
 8. The deviceaccording to claim 7, wherein the first wavelength range is not morethan 410 nm, the different types of phosphors emit red light, greenlight, and blue light, respectively, upon being excited by the light inthe first wavelength range, and the wavelength converter projects whitelight as a mixture of the red light, the green light, and the bluelight.
 9. The device according to claim 3, further comprising a firstincident optical fiber to optically connect the first semiconductorlight source to the first incident end of the photocoupler, a secondincident optical fiber to optically connect the second semiconductorlight source to the second incident end of the photocoupler, and atleast one exit optical fiber to optically connect the wavelengthconverter to the at least one exit end of the photocoupler.
 10. Thedevice according to claim 9, wherein the at least one exit end of thephotocoupler includes a first exit end and a second exit end, thephotocoupler distributes light entering the first incident end to thefirst exit end and the second exit end with substantially equal lightintensity proportions, and light entering the second incident end to thefirst exit end and the second exit end with substantially equal lightintensity proportions, the at least one exit optical fiber includes afirst exit optical fiber and a second exit optical fiber, and thewavelength converter includes a first phosphor unit optically connectedto the first exit end through the first exit optical fiber and a secondphosphor unit optically connected to the second exit end through thesecond exit optical fiber, the first phosphor unit and the secondphosphor unit having substantially equal wavelength conversioncharacteristics.
 11. The device according to claim 5, wherein thewavelength converter further includes a second phosphor, the secondphosphor being selected so as to absorb light in the second wavelengthrange to emit light having a wavelength longer than that of the light inthe second wavelength range and different from that of the light in thefirst wavelength range.
 12. The device according to claim 11, whereinthe light source device projects white light when the firstsemiconductor light source is selectively turned on, and light as amixture of the light emitted from the second semiconductor light sourceand the light emitted from the second phosphor when the secondsemiconductor light source is selectively turned on.
 13. An endoscopeapparatus comprising a light source device according to claim
 10. 14. Anendoscope apparatus comprising a light source device according to claim12.